How are electrical systems powered in an aircraft?

The correct answer reflects the multifaceted nature of an aircraft's electrical systems, which operate through multiple sources for reliability and efficiency. Aircraft typically utilize a battery as the primary source of electrical power during ground operations and emergencies. However, as the aircraft engines are started, generators become the main source of power, converting mechanical energy from the engines into electrical energy during flight. Additionally, an auxiliary power unit (APU) is often installed to provide electrical power when the engines are not running, serving as a supplemental power source when ground support is not available. This combination of battery, generators, and auxiliary power units ensures that electrical systems are powered under various operational scenarios, enhancing the aircraft’s overall reliability and safety.

Other options suggest reliance on a single source, which would not provide the necessary redundancy or operational capability needed in aviation. For example, relying solely on the battery or the APU would not support the comprehensive electrical demands of an aircraft during all phases of operation. Thus, option C accurately captures the complete range of power sources utilized for aircraft electrical systems.